Custom Model East- West.

When using custom models I expected the model to use the sides supplied for it.

Model sides facing East / West not showing custom texture file.
However North and South having correct textures, instead just showing vanilla supplied texture files. for the East / West sides.
(Despite previous versions working fine)

Steps to Reproduce:
Step 1 :Use a custom model that has worked in previous versions.
That Also has textures that are not traditionally found in vanilla
( such as but not limited to 1.8.8 )

Step 2 :Use 15w31a or b

Step 3 :Look at the East / West textures

( Note. First image is showing off the broken bit.)

Thank you for reading.